The present invention relates to an improved device for cutting venous valves.
A common method for remedying circulation disorders, particularly in the lower limbs, due to an artery whose function has been seriously reduced by, e.g., calcification consists in the application of a bypass or shunt around the impaired arterial portion by means of a suitable vein.
Since the flow in the shunt will be opposite to the normal flow direction in the vein, it is necessary to either take out and reverse the vein or remove the venous valves which have the function of non-return valves and otherwise would prevent the flow in the arterial flow direction. Such cleaning of the veins from valves is currently usually performed by means of a so-called valvulotome, which in one form consists of a generally cylinder-shaped body, the fore end of which is rounded to facilitate its insertion into and avoid damage to the vein, and the rear end of which is provided with cutting knives arranged substantially transversely to the axial direction. The valvulotome is inserted through a distal incision into the vein and advanced manually the desired distance in the passage direction of the valves. When the valvulotome is successively drawn back by means of a wire attached to the rear portion thereof, the venous valves will close and be cut off by the cutting knives. Another form of valvuotome is an angled knife which is inserted into the vein and hooked to the valve for cutting it off.
The above described valvulotomes have, however, some disadvantages. On one hand, it is not always ensured that the venous valves are held sufficiently stretched or closed when the valvulotome is drawn back for the valves to be cut to the required extent, and, on the other hand, it may sometimes occur that the vein will spasmodically contract around the valvulotome -- spasm -- with the result that the blood vessel wall may also be damaged.
For the purpose of overcoming these problems US-A-4,493,321 proposes a venous valve cutter in which the body supporting the cutting knives has been supplemented at the cutting knife end thereof with a separate leader body attached thereto in a spaced relationship by means of a thin rod, as well as with means for connecting the end of a catheter for intravenous fluid supply to be discharged at some distance from the opposite end of the cutting knives supporting body. For manoeuvring the device a flexible but torsionally rigid pulling rod is connectable to the free end of the leader body.
When using the valve cutter a distal and a proximal incision is made into either side of the vein portion to be cleaned from valves. The above mentioned pulling rod is then separately inserted through the distal incision and up along the vein until the rod end exits from the proximal incision, at which point it is attached to the cutter leader body. When the fluid supply catheter has been connected the whole assembly is then, by means of the pulling rod, slowly pulled back towards the distal incision while cutting off the venous valves passed, the fluid supplied ensuring that the valves are held completely closed during the cutting procedure and that the risk of the above mentioned spasmodic contraction of the vessel walls around the cutting body is eliminated.
Along with the relatively complex construction with several separate parts a considerable disadvantage of this device resides in the necessity of making, in addition to the distal incision, also a proximal incision into the vein, involving additional discomfort to the patient.
In EP-A1-0 248 761 another type of vein valve cutter is disclosed which also has a fluid outlet in connection with the cutting means. This vein valve cutter is in the form of a catheter, the distal end of which is provided with a plurality of cutting fingers protruding in the longitudinal direction of the catheter. The catheter is further surrounded by a telescoping sheath arranged such that it may be extended over the cutting fingers to protect the vessel walls when the catheter is advanced in the vein and be retracted and expose the cutting knives immediately prior to valve cutting. The sheath additionally has the function of defining a fluid supply channel between the sheath and the catheter, through which channel fluid may be supplied to assure closure of the valves. This vein valve cutter is primarily intended to be pushed in the vein to be cleaned, but may, e.g., for the preparation of extended vein lengths, also be pulled through the vein. For this reason the cutting end of the catheter is provided with a pulling loop, to which a pulling wire may be attached. In the last mentioned case the pulling wire will be advanced in the vein in the blood flow direction to be hooked to the catheter which is inserted through a proximal vein incision.
In addition to the fact that this vein valve cutter has a relatively complicated construction, also in this case a proximal vein incision must be made to permit the cutter to be advanced in the vein by pulling.